/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: xiaotutu
 * Date: 2024-08-06
 * Time: 10:15
 */
public class MyLinkedList {

    static class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;
    public ListNode last;

    public int size() {
        int len = 0;
        ListNode cur = head;
        while (cur != null) {
            len++;
            cur = cur.next;
        }
        return len;
    }
    // 打印
    public void display() {
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

    //查找是否包含关键字key是否在链表当中
    public boolean contains(int key) {
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    //头插法
    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        if(head == null) {
            head = node;
            last = node;
            return;
        }
        node.next = head;
        head.prev = node;
        head = node;
    }
    //尾插法
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if(head == null) {
            head = node;
            last = node;
            return;
        }
        last.next = node;
        node.prev = last;
        last = node;
    }

    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index, int data) {

    }

}
